1. Field of Invention
The present invention relates to a recoil system for guns such as field guns, howitzers and gun-howitzers and particularly, to a recoil system where the recoil distance is automatically adjusted according to the angle of barrel elevation.
2. Description of Prior Art
A problem which exists with field-type guns such as towed howitzers for example, is that of stability under recoil conditions when firing rounds at low angles of trajectory. Traditionally, high gun masses have minimized this problem in that the higher the weight of the gun, the more stable it tends to be under firing and recoil conditions. However, more recently and especially in the case of larger guns such as, for example, 155 mm towed howitzers, it has become increasingly desirable to transport the gun by helicopter in the interests of improved mobility and response time. The objectives of improved stability through increased mass and improved mobility by helicopter are mutually incompatible.
International patent application published under number WO89/06778 describes a lightweight weapon system having a recoil system which effectively increases the apparent weight of the weapon under firing and recoil conditions. The apparent weight increase is effected by causing the gun barrel and recoil mass to recoil along a curvilinear path in a rearwardly and upwardly direction. Two sets of curvilinear tracks are provided such that the ordnance in its full recoil position is substantially parallel to and above the original ordnance position prior to firing. In this manner, it is possible to make a stable and ergonomically acceptable lightweight weapon from lightweight materials such as titanium and aluminium alloys whereas before, conventional steel materials were used.
The term "ordnance" includes the barrel, breech, muzzle brake of the weapon.
However, other problems remain to be solved in that whilst a relatively long recoil distance may be employed when the gun is firing at low barrel elevations to reduce the recoil force and destabilizing moment, a relatively much shorter recoil distance is advisable when the gun is used at high angles of barrel elevation in order that the breech of the gun does not hit the ground. In the past such problems have been overcome by digging recoil pits into which the gun breech may recoil. Recoil pits are undesirable in that they take time to prepare so extending the time taken to put the weapon into action.
Proposals have been made in the past to shorten the recoil distance by providing mechanisms which are automatically linked to the angle of elevation of the barrel. Known recoil controlling mechanisms employ a hydro-pneumatic cylinder fixed to the ordnance and forming part of the recoil mass, a piston and valve assembly being provided in the cylinder and linked by a piston rod to a strong fixing point on the cradle relative to which the barrel moves during recoil during firing. Under recoil conditions, a high pressure of up to 8,000 to 9,000 p.s.i. can be developed in the recoil cylinder in, for example, a 155 mm howitzer weapon. This pressure is applied to a valve, within the cylinder, which is adjusted by rotation of the piston rod which is itself linked by a system of cams, bellcranks and pushrods to the gun carriage relative to which the barrel rotates during angle of elevation changes. As a result of the high hydraulic pressure generated in the recoil cylinder during firing, a torque is generated on the recoil brake piston rod which generates loads in the linkages between the piston rod and carriage which adjust the piston rod rotation. These loads lead to high rates of wear together with actual distortion of the linkage during firing. Such wear and distortion inevitably results in poor control of orifice size and consequential poor control of the recoil pressure and recoil distance and in the worst case may result in component failure and the gun breech hitting the ground.
It must be understood that, that for the same charge, substantially the same recoil energy must be dissipated whether the gun is being fired at a low angle of elevation where a relatively long recoil distance is available or at a high angle of elevation where a relatively short recoil distance is available. Thus, the pressure generated in the recoil cylinder at high angles of barrel elevation are greater than those at low angles of barrel elevation. Higher recoil pressure corresponds to higher recoil force.